As a recording method using an ink-jet printer, various kinds of diverse ink jetting systems have been developed, and for recording in these systems, ink droplets are generated and deposited to various recording materials (paper, film, cloth etc.).
A recording method via an ink-jet printer has characteristics such that no sound is produced since there is no contact between a recording head and a recording material and this method can print on a variety of substrates such as a substrate having uneven surfaces, a substrate comprising a soft material, and a fragile substrate. Recently, ink-jet printers are spread rapidly since it is easy to reduce their size, to print with a high speed and to make color prints. They are expected to be further popularized significantly.
In order to record in color picture or character informations on a color display of a computer via an ink-jet printer, a subtractive mixture method with four inks comprising three primary coloring matters of yellow (Y), magenta (M) and cyan (C) and additionally black (K) is generally adopted. To reproduce a subtractive mixed color image as faithfully as possible by a subtractive mixed color image of red (R), green (G) and blue (B) for CRT displays etc., it is desired that coloring matters used, particularly coloring matters used in YMC inks, have hues as near as possible to standard hues of YMC and are as vivid as possible. And, an ink composition is requested to be stable for a long-period storage and to give prints having a high concentration and excellent in fastnesses such as water resistance, light resistance, and ozone resistance. Prints resulting from recording via an ink-jet printer will be applied for display such as advertisement in order to broaden an application of an ink composition. In such cases, prints will be often exposed to light (an electric lamp, a fluorescent lamp, a sunlight and the like) and an air (containing nitrogen oxide gas, ozone gas and the like). Thus, an ink composition giving printed images excellent in ozone resistance is especially requested. Many images printed on coated papers via an ink-jet printer are faded by ozone. Reason considered is an interaction between an ozone gas in an air and inorganic substances and/or polymers applied on coated papers, but it is not correctly elucidated at present. The present invention relates to a magenta ink among inks having the above hues.
The application of ink-jet printers is broadened from small printers for OA to large printers for industry, and a chance to expose prints outdoors is increasing. Thus, the improvement of fastnesses such as water resistance, light resistance, and ozone resistance is further requested. Among these properties, water resistance is under significant improvement by coating, together with PVA resin, organic or inorganic fine particles (e.g. cationic polymer, porous silica, alumina sol and special ceramics) capable of adsorbing coloring matters in ink, onto the surface of the paper. In practice, such papers have been commercially available as various coated papers for ink-jet printing. However, a technique significantly improving light resistance and ozone resistance has not been established yet. If prints resulting from printing on coated papers called as glossy papers are left in a well ventilated place, they are faded and discolored. In order to resolve this problem, prints are processed by laminating after printing so as to prevent them from fading at present. However, this method has many demerits in time, convenience and cost. To provide a fundamental method for improving the above problem, the development of a magenta dye which is hardly faded is an important problem.
Representative skeletons of a magenta coloring matter used in a water-based ink for ink-jet recording are xanthene as described in JP-A-54089811 (1979), JP-A-08060053 (1996), JP-A-08143798 (1996) and the like; and azo having H acid in its skeleton as described in JP-A-61062562 (1986), JP-A-62156168 (1987), JP-A-03203970 (1991), JP-A-07157698 (1995), JP-B-07078190 (1995) and the like. However, xanthene coloring matter have very poor light resistance although they are very excellent in hue and clarity. While, azo coloring matter having H acids in their skeletons have poor light resistance and clarity although they have good hue and water resistance. As described in JP-A-03203970 (1991), an azo magenta dye excellent in clarity and light resistance has been developed, but its light resistance is still insufficient as compared with dyes having other hues such as a cyan dye, a representative of which is a cupper phthalocyanine dye, a yellow dye and the like. And, prints resulting from printing with these coloring matters on glossy papers may be discolored and faded even if they are left in a well ventilated place.
Further, as a magenta coloring matter excellent in clarity and light resistance, coloring matters having anthrapyridone skeleton as described in JP-A-59074173 (1984), JP-A-02016171 (1990) and the like are known, but they do not meet all requirements of hue, clarity, light resistance, water resistance, ozone resistance and a solution stability.
An object of the present invention is to provide a water-based magenta ink composition having a hue and clarity suitable for ink-jet recording and gives prints excellent in fastnesses such as a light resistance, and an ozone resistance.